A remote keyless entry system or a smart entry system used for various types of operations such as locking and unlocking a car door is coming to widespread use. In a remote keyless entry system, a transmission device carried by a user sends a radio wave that contains a prescribed code to a reception device placed on a car. Subsequently, the reception device receives this radio wave, and locks or unlocks a door only when the code stored in a memory of a control device placed on a car matches with the prescribed code mentioned above.
Some reception devices are provided with an antenna coil that can receive a radio wave in three axial directions. For example, the patent document 1 discloses a technology of an antenna coil capable of receiving a radio wave in three axial directions.
[Patent document 1] WO2005/088767 [Refer to FIGS. 1, 5 and 6]